Boys of that age should not be sexual with each other. Any condoning of that behavior is not helpful. While some curiosity or experimentation may be seen as 'normal', how do the ideas get put into their head?? What is more common at that age is discovering your OWN body and sensation that feels good. Introducing others into it indicates that a child has had it done to them first by someone else or seen it. Neither is good. And at that point, parents step in. NO ONE touches your private parts and you touch your own in your own room when alone. That's a good rule for kids. You don't give a lot of details but oversexualized children especially at 8 years old is usually not a good sign.